1. Field of the Invention
The present invention relates to a method for producing high amounts of Monascus pigment by cultivating a Monascus species in particularly prepared media to which rice powder and peptone are added as carbon and nitrogen sources, respectively.
2. Description of the Related Art
Nowadays, with increasing doubts about the health safety of artificial pigments many researchers have begun to search for safe pigments to take the place of them, especially, natural pigments. Among artificial pigments, those permitted for use in developed countries like America and Japan are only a few, and the amounts of them added to food are also restricted. Among many natural pigments which come from animals, plants, and microorganisms, microbial pigments appear to be the most promising from the viewpoints of how to apply the pigments, how to produce them, and how to cultivate the producers.
Monascus sp., a fungus, which traditionally has been used in countries like China and Japan for the fermentative production of red wine and red soybean cheese, attracted great interest with respect to ease of approach.
The pigments comprising the Monascus color are rubropunctatin (C.sub.21 H.sub.22 O.sub.5 -red color), monascorubrin(C.sub.23 H.sub.26 O.sub.5 -red color), monascin(C.sub.21 H.sub.26 O.sub.5 -yellow color), ankaflavin(C.sub.23 H.sub.30 O.sub.5)-yellow color), rubropunctamine(C.sub.21 H.sub.23 NO.sub.4 -purple color), and monascorubramine(C.sub.23 H.sub.27 NO.sub.4 -purple color) (Y. C. Su, Kor. J. Appl. Microbiol. Bieng., 11, 325, 1983).
Tadao Hiroi made it clear by his test that a Monasous species produces none of aflatoxin B.sub.1, B.sub.2, G.sub.1, and G.sub.2. And also, from the reversion plate test, it was not observed that the pigments work as frame shift mutagens. Rec-assay with Bacillus subtilis H-17 and M-45, in addition, confirmed the negative effect of the pigments on DNA-destruction. Furthermore, rats fed on the pigments were reported not to be harmed (H, Tadao, New Food Industry, 30, 1, 1988).
The proof that the Monascus pigments are safe to health brought many researchers including Hiroi to efforts to produce high amounts of them. They have, as often as not, pointed out that attention must be paid to the compositions of the media, above all, to nitrogen sources. According to the study of Carel and Shepherd, an oxidized nitrogen increases the yield of the purple pigments, that is, rubropunctamine and monascorubramine, and a reduced nitrogen increases that of the red pigments such as rubropunctatin and monascorubrin. It is also said that organized nitrogens are very effective for the growth of Monascus species while not effective for high production of the pigments. A nitrate stimulates asexual propagation followed by conidiation, and an ammounium stimulates sexual propagation accompanied by the formation of cleistothecia(M. Carel and D. Shepherd, Can. & Microbiol., 23, 1360, 1977). If the above report by Su that the production of Monascus pigments increases by inhibition of conidiation is considered, it will not be favorable to the production of the pigments to cultivate the Monascus sp. in a medium containing a nitrate. Therefore, it is believed that high production of Monascus pigments will assured if a Monascus sp. propagates sexually more often than asexually, if a reduced nitrogen is contained in the medium used, and if suitable growth is guaranteed.